Petrogenesis of the Dog Lake Granite Chain, Quetico Basin, Superior Province, Canada: Implications for Neoarchean crustal growth

Abstract

The Neoarchean Dog Lake Granite Chain consists of six intrusions (Shabaqua, Silver Falls, Trout Lake, Barnum Lake, White Lily, and Penassen Lake), which parallel the tectonic boundary between the Abitibi-Wawa terrane to the south, and the Quetico Basin to the north. It is a single composite body at depth with derivative branches extending higher into the crust, and consists of three phases: monzodiorite, syenite/quartz monzonite and granite, emplaced at approximately 2.671 Ga, 2.663–2.669 Ga and 2.670 Ga, respectively.The metaluminous monzodiorites with abundant angular igneous mafic xenoliths, enriched zircon ɛHf(t) values ranging from −0.52 to +4.20 and enriched ɛNd(t) (−0.37 to +1.74), were generated by assimilation fractional crystallization of a mafic magma generated by partial melting of enriched mantle metasomatized by melts of subducted oceanic sediments. The metaluminous syenite/quartz monzonite phase has similar mineral assemblages, trace element and Nd-Hf isotopic characteristics to the monzodiorite, and was probably produced by assimilation fractional crystallization of a monzodiorite magma. The granite-hosted zircons have prominent positive Ce anomalies, negative Eu anomalies and mostly positive zircon ɛHf(t) (−0.12 to +4.25) and enriched ɛNd(t) values (−1.70 to +0.71), suggesting a mixed source of immature sedimentary rocks and metasomatically enriched mantle-derived magma.The subduction of oceanic lithosphere under the Abitibi-Wawa arc during the collision of the Abitibi-Wawa arc and the Wabigoon terrane before ~2.7 Ga, generated a metasomatically enriched mantle and associated volcanic rocks. The volcanic rocks underwent rapid weathering and erosion to form the immature sedimentary rocks of the Quetico accretionary prism. Lithospheric inversion caused partial melting of the metasomatically enriched mantle, generating a mafic magma. The mafic magma ascended and underwent assimilation fractional crystallization forming the monzodiorite and syenite/quartz monzonite. Mafic magma was emplaced at the base of the Archean immature sedimentary rocks, triggering melting to generate felsic magma. Mixing of these felsic and mafic magmas generated the DLGC granite in the shallow crust.The Neoarchean arc-continent collision preserved in the Quetico Basin is similar to that in modern arc systems where intra-oceanic arc crust is added to continental margins, suggesting it was an important mechanism for recycling juvenile crust, generating compositional differentiation, and cratonization.